Current application of "high-dose" steroid therapy for CNS injury. A pharmacological perspective

Experimental and clinical studies of eicosanoids in cerebrospinal fluid after spinal cord injury

OBJECTIVE

In an attempt to elucidate a possible role for eicosanoids in the pathogenesis of spinal cord injury (SCI), we measured the concentration of leukotriene (LT) C4, thromboxane B2, and 6-keto-prostaglandin F1 alpha in cerebrospinal fluid in both a canine experimental model and 11 patients with SCIs.

METHODS

The eicosanoid concentration in cerebrospinal fluid was measured by radioimmunoassay. Neurological severity was assessed according to the grading system of Frankel et al.. Control samples were obtained from 20 patients without SCIs.

RESULTS

In the canine model, a significant increase in all eicosanoid levels was found on Days 1 to 7, which subsequently returned to the control levels. In the clinical study, the highest mean (+/- standard error of the mean) concentrations of LTC4, thromboxane B2, and 6-keto-prostaglandin F1 alpha in the acute stage of SCI were 95.9 +/- 10.7, 175.2 +/- 38.2, and 167.5 +/- 39.9 pg/ml, respectively. These concentrations were five to nine times higher than control levels. There was a good correlation between cerebrospinal fluid LTC4 levels and the neurological severity. The time-dependent change in LTC4 concentrations in seven patients with SCIs was similar to that observed in the canine model. In addition, the highest mean concentrations of the eicosanoids measured in patients with complete paralysis was also similar to those of the canine model. The eicosanoid concentrations in five patients with SCI were measured more than 6 months after the onset of injury. Although all eicosanoid levels had elevated in the acute stage of injury, they were not elevated and showed the same levels as the controls at the chronic stage.

CONCLUSION

The findings suggest that enhanced arachidonate metabolism occurs in humans and support the evidence from animal experiments that emphasizes the importance of eicosanoids in the secondary processes mediating ischemia and edema.

Stress, Glucocorticoids, and Damage to the Nervous System: The Current State of Confusion

An extensive literature demonstrates that glucocorticoids (GCs), the adrenal steroids secreted during stress, can have a broad range of deleterious effects in the brain. The actions occur predominately, but not exclusively, in the hippocampus, a structure rich in corticosteroid receptors and particularly sensitive to GCs. The first half of this review considers three types of GC effects: a) GC-induced atrophy, in which a few weeks' exposure to high GC concentrations or to stress causes reversible atrophy of dendritic processes in the hippocampus; b) GC neurotoxicity where, over the course of months, GC exposure kills hippocampal neurons; c) GC neuroendangerment, in which elevated GC concentrations at the time of a neurological insult such as a stroke or seizure impairs the ability of neurons to survive the insult. The second half considers the rather confusing literature as to the possible mechanisms underlying these deleterious GC actions. Five broad themes are discerned: a) that GCs induce a metabolic vulnerability in neurons due to inhibition of glucose uptake; b) that GCs exacerbate various steps in a damaging cascade of glutamate excess, calcium mobilization and oxygen radical generation. In a review a number of years ago, I concluded that these two components accounted for the deleterious GC effects. Specifically, the energetic vulnerability induced by GCs left neurons metabolically compromised, and less able to carry out the costly task of containing glutamate, calcium and oxygen radicals. More recent work has shown this conclusion to be simplistic, and GC actions are shown to probably involve at least three additional components: c) that GCs impair a variety of neuronal defenses against neurologic insults; d) that GCs disrupt the mobilization of neurotrophins; e) that GCs have a variety of electrophysiological effects which can damage neurons. The relevance of each of those mechanisms to GC-induced atrophy, neurotoxicity and neuroendangerment is considered, as are the likely interactions among them.

Treatment of patients with severe head injury by triamcinolone: a prospective, controlled multicenter clinical trial of 396 cases

The present studies were conducted to test whether the outcome of severe head injury is improved by early administration of the synthetic corticosteroid triamcinolone. In a prospective, double-blind, multicenter clinical trial, 396 patients with severe head injury were randomized to a steroid group (n = 187) receiving 200 mg triamcinolone acetonide (Volon A soluble) i.v. within 4 h after trauma, followed by 3 x 40 mg/day i.v. for 4 days, and 3 x 20 mg/day i.v. for a further 4 days, and a placebo group (n = 209) receiving injections which did not contain any active drug. The placebo group was subjected to the same standard treatment procedures. Clinical features were not different between the groups upon admission to hospital. Subdural hematoma, epidural hematoma, and focal supratentorial contusion were among the most frequent diagnoses. The result of treatment with triamcinolone was assessed at discharge from the hospital and at 1 year after trauma, using the Glasgow Outcome Scale. Differences in favor of steroid treatment could be detected with regard to the patients' condition at discharge (P = 0.0634). More patients with steroids had a good recovery (49.2% vs 40.7%), and fewer died (16.0% vs 21.5%). Differences in outcome were even more pronounced (P < 0.0145) in patients with a focal lesion and a Glasgow Coma Score on admission of < 8 (n = 93). In this group, 34.8% of the patients made a good recovery, as against 21.3% of the placebo group; mortality was also lower in the verum group (19.6% vs 38.3%). The results indicate that a major subgroup of patients with severe head injury benefits from early administration of triamcinolone. Efficacy of the treatment can be expected, in particular, in patients with a focal cerebral lesion and a Glasgow Coma Score of < 8 on admission. Administration of steroids beginning at the scene of an accident would therefore be beneficial in these cases.

Correlation of alterations on Na(+)-K+/Mg+2 ATPase activity, lipid peroxidation and ultrastructural findings following experimental spinal cord injury with and without intravenous methylprednisolone treatment

The sodium-potassium activated and magnesium dependent adenosine-5'-triphosphatase (Na(+)-K+/Mg+2 ATPase EC 3.6.1.3.) activity and lipid peroxidation and early ultrastructural findings are determined in rat spinal cord at the early stage of trauma produced by a surgical clip on the thoracal 2-7 segments. The effect of treatment with intravenous methylprednisolone (MP) was evaluated the basis of these biochemical alterations and ultrastructural findings in the same model. The specific activity of the membrane bound enzyme Na(+)-K+/Mg+2 ATPase was promptly reduced in as early as ten minutes following spinal cord injury and remained at a level lower than the levels in the control group and in the sham-operated group. Methylprednisolone treatment immediately after the trauma attenuated the inactivation of Na(+)-K+/Mg+2 ATPase. On the other hand, there was significant difference in lipid peroxide content between the sham-operated and the injured animals. Methylprednisolone treatment reduced thiobarbituric acid reactive substance (TBARS) content in Group IV. We determined a positive relationship among membrane-bound enzyme Na+K+/Mg+2 ATPase activity, malondialdehyde (MDA) content and early ultrastructural changes in the traumatized and treated groups.

Clinicopathologic effects of a 21-aminosteroid compound (U74389G) and high-dose methylprednisolone on spinal cord function after simulated spinal cord trauma

A model simulating acute-compressive spinal cord trauma at the second lumbar spinal cord segment (100 g, 300 seconds) was used to evaluate the efficacy of a vehicle control, methylprednisolone sodium succinate (MPSS), and a 21-aminosteroid compound (U74389G). Dogs were allocated into one of five treatment groups (A to E) using ultrasonographic determination of spinal cord diameters to ensure even distribution of spinal cord diameters among the treatment groups. Initial dosages of the vehicle control (A), methylprednisolone (30 mg/kg of body weight) (B), or U74389G (30 mg/kg, 3 mg/kg, or 10 mg/kg of body weight) (C, D, or E, respectively) were administered intravenously 30 minutes after trauma. Dosages were reduced by one-half for 2 and 6 hour treatments. Then every 4 hours for 42 hours, dosages were reduced one-third and one-sixth from the original dose of methylprednisolone and U74389G, respectively. Neurological examinations were performed daily for 21 days. Histopathological examination of the traumatized spinal cord showed malacic and degenerative lesions. Although significant differences in some portions of the neurological and histopathologic examinations were observed, clinical efficacy for MPSS and U74389G could not be established in this model.

[Clinical experiences and results of high-dosage methylprednisolone therapy in spinal cord trauma 1991 to 1993]

Studies in animals and especially the NASCIS II study illustrated the neuroprotective effects of methylprednisolone, but they are disputed. At the University Clinic of Traumatology, Vienna, 31 patients with spinal cord injuries were given methylprednisolone as a bolus of 30 mg/kg body weight followed by a maintenance dose of 5.4 mg/kg body weight/h for another 23 hours. Twenty-seven patients were stabilised within 8 hours, 2 patients were not operated on, because of their low prognosis. Two patients could be treated conservatively, because the spinal fractures were supposed to be stabile. Then follow-up studies of these patients were between 1 and 3.2 years. All patients (100%) with incomplete neurologic deficits (n = 18) showed a significant recovery and even 3 patients (23.1%) with primarily a complete tetraplegia (n = 13) showed a nearly entire recovery. Compared to these results we look back at 113 patients with complete and incomplete neurologic deficits who were treated at the I. University Clinic of Traumatology, Vienna, and would have got methylprednisolone following our current management procedures.

Traumatic optic neuropathy

Knowledge concerning the pathophysiologic mechanisms of traumatic optic neuropathy is limited. The optic nerve is a tract of the brain. Therefore, the cellular and biochemical pathophysiology of brain and spinal cord trauma and ischemia provide insight into mechanisms that may operate in traumatic optic neuropathy. The dosage of methylprednisolone (30 mg/kg/6 hours) which was successful in the National Acute Spinal Cord Injury Study 2 (NASCIS 2) evolved from the unique pharmacology of corticosteroids as antioxidants. The management of traumatic optic neuropathy rests on an accurate diagnosis which begins with a comprehensive clinical assessment and appropriate neuroimaging. The results of medical and surgical strategies for treating this injury have not been demonstrated to be better than those achieved without treatment. The spinal cord is a mixed grey and white matter tract of the brain in contrast to the optic nerve which is a pure white matter tract. The treatment success seen with methylprednisolone in the NASCIS 2 study may not generalize to the treatment of traumatic optic neuropathy. Conversely, if the treatment does generalize to the optic nerve, NASCIS 2 data suggests that treatment must be started within eight hours of injury, making traumatic optic neuropathy one of the true ophthalmic emergencies. Given the uncertainties in the treatment, ophthalmologists involved in the management of traumatic optic neuropathy are encouraged to participate in the collaborative study of traumatic optic neuropathy.

Efficacious experimental stroke treatment with high-dose methylprednisolone

BACKGROUND AND PURPOSE

Recent studies reveal success in treating spinal cord trauma with early, high-dose methylprednisolone. As in spinal cord research, failure to find therapeutic effects with steroids in studies of acute stroke treatment may reflect institution of treatment too late and at too low dosage. We presently test the efficacy of stroke treatment with methylprednisolone administered early and at high doses using a cat temporary middle cerebral artery occlusion model.

METHODS

We occluded the middle cerebral artery for 4 hours in 24 pentobarbital-anesthetized cats. To enhance the probability of brain injury, we maintained the cats' serum glucose concentrations at high levels both during occlusion and for 6 hours afterward. Using a blinded, randomized study design, we treated 12 cats with methylprednisolone (30 mg/kg IV infused over 15 minutes starting 30 minutes after occlusion followed by 5.4 mg.kg-1.h-1 IV for the next 23 hours) and 12 control cats with vehicle. During and for 8 hours after occlusion, we monitored cerebral blood flow, brain and rectal temperatures, and multiple cardiovascular and blood compositional parameters. We assessed brain pathological outcome after animal survival for 4 days or after acute death from hemispheric edema.

RESULTS

Experimental and control animals showed similar early mortality rates (treated, 3/12; controls, 4/12). However, surviving methylprednisolone-treated cats (n = 9) showed a mean infarct size more than six times smaller than in the control animals (n = 8) (mean +/- SEM, 2.4 +/- 0.7% versus 15.6 +/- 6.2% of the ischemic territory, respectively; P < .05). The methylprednisolone-treated animals also showed less marked reduction in cerebral blood flow during ischemia than did the controls (mean +/- SEM, 58 +/- 5% versus 74 +/- 4%; P < .005).

CONCLUSIONS

Administering methylprednisolone at high doses early after onset of ischemia significantly reduces tissue injury in cats that survive 4 days of temporary middle cerebral artery occlusion. This improvement in outcome occurs in the setting of significant increases in ischemic cerebral blood flow. However, methylprednisolone treatment did not reduce hemispheric edema in animals that died early after temporary middle cerebral artery occlusion.

Effect of endotoxin on tirilazad mesylate (U74006F) pharmacokinetic parameters in neonatal calves

The pharmacokinetics of the 21-aminosteroid tirilazad mesylate (U74006F) were studied in both healthy and endotoxin-challenged neonatal calves. Group I calves received a 3-h intravenous (i.v.) infusion of sterile saline (250 ml) and tirilazad mesylate (1.5 mg/kg i.v.) 1 h after the start of the saline infusion. Group II calves received tirilazad mesylate 1 h after the start of a 3-h endotoxin (3.25 micrograms/kg) infusion. The data obtained indicate that tirilazad mesylate follows a biexponential equation in neonatal calves. The area-derived volume of distribution (Vdarea) was 9.68 +/- 0.759 l/kg in healthy calves and 6.53 +/- 1.20 l/kg in endotoxin-challenged calves (P < 0.05). Similarly, significant (P < 0.05) decreases in steady-state volume of distribution (Vdss) and central volume (Vc) were observed in endotoxin-challenged calves (5.32 +/- 0.979 l/kg and 1.68 +/- 0.189 l/kg, respectively) compared to healthy calves (7.58 +/- 0.834 l/kg and 2.43 +/- 0.452 l/kg, respectively). A and B were significantly larger in endotoxin-challenged calves than in healthy calves (P < 0.05). Rate constants and their associated half-lives, area under the curve and clearance were not significantly altered by endotoxin challenge. Serum thromboxane generation (ex vivo) was evaluated as a marker of the drug's physiologic activity. There was no significant difference in thromboxane generation during clotting of blood from healthy and endotoxemic calves treated with tirilazad mesylate.

Methylprednisolone therapy in laser injury of the retina

The efficacy of methylprednisolone in argon-laser-induced retinal injury in primates was evaluated by clinical, histopathologic, and morphometric criteria. Methylprednisolone was given with a loading dose of 30 mg/kg followed by 5.4 mg/kg per hour in three different regimens: (1) starting 24 h before laser and continuing for 4 days; (2) starting immediately after laser and continuing for 4 days; and (3) starting immediately after laser and continuing for 8 h. Fundus photography, fluorescein angiography, and histologic examination showed significant beneficial effects of all three treatments compared to controls. Morphometrically, at the center of the lesion, the width of disrupted outer nuclear layer, the width of the affected RPE, and the percentage of residual photoreceptor nuclei confirmed the efficacies of treatment regimens 1 and 2, but not treatment regimen 3.

Inhibition of inflammatory cell-mediated myelin oxidation and interleukin-1 beta generation by a 21-aminosteroid, U74500A

Inflammatory cell-mediated myelin injury may be an important cause of tissue damage in both acute and chronic central nervous system (CNS) disorders. The 21-aminosteroids are novel derivatives of methylprednisolone without obvious glucocorticoid or mineralocorticoid side effects. We evaluated the ability of 21-aminosteroid, U74500A, to inhibit oxidation of rat brain myelin by human polymorphonuclear leukocytes (PMN) and monocytes. Myelin samples, as confirmed by SDS-PAGE, were incubated with PMN or monocytes and 100 microM U74500A or vehicle. Myelin oxidation by both PMN and monocytes was significantly reduced by U74500A. These observations demonstrate that U74500A can inhibit myelin oxidation by inflammatory cells. Additionally, 100 microM U74500A significantly reduced production of interleukin 1-beta by monocytes exposed to myelin. The aminosteroids may be beneficial in CNS disorders where myelin injury by inflammatory cells appears to contribute, such as acute focal ischemia or multiple sclerosis.

Limiting ischemic spinal cord injury using a free radical scavenger 21-aminosteroid and/or cerebrospinal fluid drainage

Traumatic spinal cord injury occurs in two phases: biomechanical injury, followed by ischemia and reperfusion injury. Biomechanical injury to the spinal cord, preceded or followed by various pharmaceutical manipulations or interventions, has been studied, but the ischemia/reperfusion aspect of spinal cord injury isolated from the biomechanical injury has not been previously evaluated. In the current study, ischemia to the lumbar spinal cord was induced in albino rabbits via infrarenal aortic occlusion, and two interventions were analyzed: the use of U74006F (Tirilazad mesylate), a 21-aminosteroid, and cerebrospinal fluid (CSF) drainage. These treatment modalities were tested alone or in combination. In Phase 1 of this study, the rabbits received 1.0 mg/kg of Tirilazad or an equal volume of vehicle (controls) prior to the actual occlusion, three doses of Tirilazad (1 mg/kg each) during the occlusion, then several doses after the occlusion. Of the Tirilazad-treated animals, 30% became paraplegic while 70% of the control animals became paraplegic. Phase 2 involved the same doses of Tirilazad as in Phase 1 and, in addition, CSF pressure monitoring and drainage were performed. The paraplegia rate was 79% in the control animals, 36% in the group receiving Tirilazad alone, 25% in the group with CSF drainage alone, and 20% in the Tirilazad plus CSF drainage group. This rate also correlated with changes noted in CSF pressure; both Tirilazad administration alone and CSF drainage alone induced a decrease in CSF pressure and the two combined produced a further decrease. There was marked improvement in the perfusion pressure when using Tirilazad alone, CSF drainage alone, and Tirilazad therapy in combination with CSF drainage, with the last group producing the largest increase. This change in CSF pressure and perfusion pressure correlated with improved functional neurological outcome. Pathological examination revealed that Tirilazad therapy reduced the extensive and diffuse neuronal, glial, and endothelial damage to (in its most severe form) a more patchy focal region of damage in the gray matter. Cerebrospinal fluid drainage resulted in pyknosis of some motor neurons, and some eosinophilia. The combination of CSF drainage and Tirilazad administration resulted in the least abnormality, with either normal or near-normal spinal cords. It is concluded that Tirilazad administration decreased CSF pressure during spinal cord ischemia and reperfusion and, like CSF drainage, increased and improved the perfusion pressure to the spinal cord, decreased spinal cord damage, and improved functional outcome.(ABSTRACT TRUNCATED AT 400 WORDS)

A comparison of the protective effect of dexamethasone to other potential prophylactic agents in a neonatal rat model of cerebral hypoxia-ischemia

It has recently been reported that pretreatment with a single dose of dexamethasone (0.1 mg/kg) 24 hours before hypoxia in 7-day-old rat pups is protective against an hypoxic-ischemic insult (unilateral carotid artery occlusion followed by 3 hours of hypoxia in 8% O2). The authors now examine whether pretreatment 6 hours before insult is equally effective and compare other agents potentially suitable for prophylaxis in neonatal hypoxia-ischemia, including the calcium antagonists flunarizine (30 mg/kg pretreatment), nimodipine (0.5 mg/kg pretreatment), and the 21-aminosteroid U-74389F (10 mg/kg pre- and posttreatment). For each active agent, there was also a vehicle-treated control group. Comparison of the mean area of ipsilateral infarction on brain coronal sections showed that there was no statistically significant difference between the various control groups (mean area of infarction 66% +/- 4%). Pretreatment with dexamethasone 6 hours prior to hypoxia offered complete protection with no infarction. A beneficial effect was seen following pretreatment with flunarizine (mean area of infarction 33.6% +/- 7.8%), although this degree of damage was still significantly different from that seen with dexamethasone pretreatment. Pretreatment with nimodipine or U-74389F offered no protection (mean area of infarction 77.5% +/- 4% and 59% +/- 10%, respectively). Unlike findings in adult animals and clinical studies, the current studies show that dexamethasone may have a role in the treatment of neonatal hypoxia-ischemia and deserves reappraisal.

Spinal cord blood flow and evoked potential responses after treatment with nimodipine or methylprednisolone in spinal cord-injured rats

This study examined the effect of nimodipine or methylprednisolone on spinal cord blood flow (SCBF) and electrophysiological function after spinal cord injury in rats. Three groups of male rats (n = 10 per group) were injured by compression of the cord at T1 for 1 minute with a 52-g clip. The hydrogen clearance technique was used to measure SCBF at the T1 segment. Motor and somatosensory evoked potentials were recorded. SCBF and evoked potentials were measured before injury and again at approximately 1 and 2.5 hours after injury. The methylprednisolone group received a bolus of methylprednisolone (30 mg/kg) at 5 minutes after injury and then at 15 minutes after injury, the group received an infusion of methylprednisolone at 5.4 mg/kg per hour. The nimodipine group received placebo at 5 minutes and then received an infusion of nimodipine at 0.02 mg/kg per hour at 15 minutes. The placebo group received placebo at both times. Physiological parameters were closely monitored and maintained within the normal range. Albumin was administered after injury to maintain mean arterial blood pressure at or above 80 mm Hg. The infusions were continued for approximately 3 hours after spinal cord injury. SCBF was not significantly different between the experimental groups at either 1 or 2.5 hours postinjury (P = 0.16 and 0.71, respectively), and evoked potential responses did not return in any rat at any time after injury. Thus, this experiment failed to demonstrate an improvement in SCBF or electrophysiological function with either drug.(ABSTRACT TRUNCATED AT 250 WORDS)

Methylprednisolone reduces excitatory amino acid release following experimental spinal cord injury

Administration of methylprednisolone within several hours after injury to the spinal cord has been shown to reduce subsequent impairment in humans and experimental animals. Secondary damage following initial trauma is probably caused in part by the toxicity of released excitatory amino acids. We demonstrate here that methylprednisolone reduces the release of excitatory amino acids following experimental spinal cord injury in rats.

Improving the outcome of severe head injury with the oxygen radical scavenger polyethylene glycol-conjugated superoxide dismutase: a phase II trial

Formation of the oxygen radical superoxide anion is one of the final events of several metabolic pathways in the cascade that leads to delayed neuronal death after traumatic or ischemic brain injury. In the laboratory, scavenging of the superoxide anion with native superoxide dismutase (SOD) or polyethylene glycol (PEG)-conjugated SOD (PEG-SOD) has been shown to be beneficial in several types of traumatic and ischemic injury. Accordingly, PEG-SOD was utilized in a randomized controlled Phase II trial to evaluate its safety and efficacy in severely head-injured patients with a Glasgow Coma Scale score of 8 or less. At two institutions, 104 patients were randomly assigned to receive either placebo or PEG-SOD (2000, 5000, or 10,000 U/kg) intravenously as a bolus, an average of 4 hours after injury. Prognostic factors were evenly distributed in the four groups, except for mean age which was significantly higher in the group receiving 10,000 U/kg than in the placebo group (mean age 34 years vs. 25 years). No complications attributed to the study medication were noted. The average intracranial pressure (ICP) was similar in the four groups, but the percentage of time during which ICP was above 20 mm Hg was less in the groups receiving 5000 or 10,000 U/kg of PEG-SOD. Patients in the group receiving 10,000 U/kg also required less mannitol for ICP control than the placebo group. Outcome was assessed using the Glasgow Outcome Scale at 3 and 6 months postinjury in 91 and 93 patients, respectively, by blinded observers not involved in the clinical management of the patients. At 3 months, 44% of patients in the placebo group were vegetative or had died, while only 20% of patients in the group receiving 10,000 U/kg of PEG-SOD were in these outcome categories (p < 0.03, multiple logistic regression test); at 6 months, these figures were 36% and 21%, respectively (p = 0.04). Differences in outcome between the placebo group and either of the other two dosage groups were not statistically significant. It is concluded that PEG-SOD was generally well tolerated and appears promising in improving outcome after severe head injury. A larger, multicenter, Phase III trial, using a higher dose (20,000 U/kg) compared to placebo and to 10,000 U/kg of PEG-SOD is planned.

Retinal toxicity of intravitreal lazaroid (21-aminosteroid U75412E)

The 21-aminosteroids or lazaroids are a novel series of compounds being developed for the acute treatment of traumatic or ischemic injury of the nervous system. These compounds were specifically designed to localize within cell membranes and inhibit lipid peroxidation reactions. In this study, 21-aminosteroid U75412E was injected into the vitreous body of rabbit eyes to evaluate its suitability for intraocular injection and its toxicity on intraocular tissues. Doses ranged from 20 micrograms to 200 micrograms. Retinal toxicity was determined through light and transmission electron microscopy and electroretinography. No retinal toxicity was noted in doses of 30 micrograms and below.

Altered expression of NGF and P75 NGF-receptor by fibroblasts of injured teeth precedes sensory nerve sprouting

Profuse sprouting of sensory nerve fibers occurs in tooth pulp by 1-4 days following dentin injury. A possible role for nerve growth factor (NGF) in that neural response is suggested here by the demonstration that NGF mRNA and protein are increased 6 hr after injury to adult rat molars. The enhanced expression of NGF mRNA was localized to fibroblasts underlying the injury. A concomitant depletion of mRNA encoding the 75 Kd NGF receptor (NGFR) was observed in those fibroblasts. The increase in NGF mRNA was transitory and mRNA levels fell below normal levels by 2 days after injury. Both NGF and NGFR mRNA remained low thereafter in injured pulp. The inverse shifts in fibroblastic mRNA encoding NGF and NGFR were not affected by prior denervation of the tissue, or by pretreatment with dexamethasone. The regulatory mechanisms therefore must involve endogenous, non-neuronal, non-inflammatory factors that are released in response to injury.

The neuroprotective pharmacology of methylprednisolone

A 24-hour intensive intravenous dosing regimen with the glucocorticoid steroid methylprednisolone has recently been shown to be effective in enhancing neurological recovery in spinal cord-injured patients when initiated within 8 hours after injury. The state of knowledge concerning the neuroprotective pharmacology of methylprednisolone, including mechanism(s) of action, dosing requirements, and time-action considerations is reviewed, as are the results of studies with high doses in experimental and clinical head injury, subarachnoid hemorrhage, and cerebral ischemia. A primary neuroprotective mechanism of action in each of these cases is hypothesized to involve the ability of high doses of methylprednisolone to inhibit oxygen free radical-induced lipid peroxidation, although additional mechanisms may contribute. Unresolved issues are also addressed, including the therapeutic window, optimum duration of treatment, and rational combination with other neuroprotective agents. A newer methylprednisolone pro-drug with improved solution stability is discussed, together with a brief consideration of novel nonglucocorticoid steroids that surpass methylprednisolone's lipid antioxidant effects without unwanted glucocorticoid properties.

Blocking weight-induced spinal cord injury in rats: therapeutic effect of the 21-aminosteroid U74006F

The effect of the 21-aminosteroid U74006F on neurologic recovery after a spinal cord compression trauma was investigated in rats. The compression was induced by a blocking weight technique, in which a 35 g (moderate injury) or a 50 g (severe injury) weight was applied for 5 minutes to an 11 mm2 plate over the midthoracic spinal cord. One hour after trauma, the severely injured animals were treated either with U74006F, 3 mg/kg, methylprednisolone, 30 mg/kg, or vehicle, whereas the moderately injured animals received U74006F, 3 mg/kg or vehicle. Neurologic hind limb function was evaluated by the inclined plane technique. On day 1 after trauma, subtotal paraparesis occurred in the 35 g group treated with vehicle (31 +/- 1 degrees, mean +/- SEM) on the inclined plane vs 64 +/- 1 degrees before trauma) and complete paraplegia in the 50 g group (22 +/- 1 degrees). Treatment with U74006F resulted in less hind limb weakness in the 35 g group (42 +/- 2 degrees) but had no beneficial effect in the 50 g group (25 +/- 2 degrees). Neurologic function gradually improved in the 35 g groups over the 9-day observation period. However, those animals treated with U74006F were significantly better over the entire period. In the 50 g group, no recovery from paraplegia was noted over the 4 day observation period in any of the three groups. These results suggest that after weight-induced spinal cord trauma, U74006F is associated with improved neurologic function in moderately injured, but not severely injured animals.

Treatment of traumatic optic neuropathy with corticosteroids

We treated 21 patients (22 eyes) with traumatic optic neuropathy by using intravenous megadose methylprednisolone (13 patients) or high-dose dexamethasone (eight patients). Of 13 patients treated with megadose methylprednisolone, 12 had improved visual function, as did seven of nine eyes treated with intravenous dexamethasone. This difference was not significant (P = .3). Initial total blindness, mechanism of injury, or time from injury to treatment did not correlate with visual improvement.

Cerebrospinal fluid physiology and the management of increased intracranial pressure

Increased intracranial pressure can result in irreversible injury to the central nervous system. Among the many functions of the cerebrospinal fluid, it provides protection against acute changes in venous and arterial blood pressure or impact pressure. Nevertheless, trauma, tumors, infections, neurosurgical procedures, and other factors can cause increased intracranial pressure. Both surgical and nonsurgical therapeutic modalities can be used in the management of increased intracranial pressure attributable to traumatic and nontraumatic causes. In patients with cerebral injury and increased intracranial pressure, monitoring of the intracranial pressure can provide an objective measure of the response to therapy and the pressure dynamics. Intraventricular, intraparenchymal, subarachnoid, and epidural sites can be used for monitoring, and the advantages and disadvantages of the various devices available are discussed. With the proper understanding of the physiologic features of the cerebrospinal fluid, the physician can apply the management principles reviewed herein to minimize damage from intracranial hypertension.

Thyrotropin releasing hormone augments growth of spinal cord transplants in oculo

The effects of thyrotropin releasing hormone (TRH) on spinal cord growth were evaluated using the in oculo transplant model. The growth of fetal spinal cord allografts, placed into the anterior eye chamber of Sprague-Dawley rats, was markedly augmented by acute exposure of the graft and host animal to TRH at the time of transplantation. No significant growth augmentation was seen after equimolar administration of a mixture of the amino acids that comprise the TRH molecule. It is concluded that acutely administered TRH, at the time of grafting, elicits a significant stimulation of the growth of spinal cord tissue. Our data strengthen the rationale for continued clinical trials of this peptide in spinal cord injury.

Effects of treatment with U-74006F on neurological outcome following experimental spinal cord injury

The compound U-74006F is one of a series of 21-aminosteroids that lack glucocorticoid or mineralocorticoid activity. These potent inhibitors of lipid peroxidation have been specifically developed for the acute treatment of central nervous system trauma and ischemia. This study evaluated the dose-response characteristics and capability of U-74006F to promote functional recovery in cats subjected to compression trauma of the upper lumbar (L-2) spinal cord. Thirty minutes following injury, randomized and investigator-blinded treatment was initiated with the intravenous administration of either vehicle (citrate-buffered saline) or one of eight doses of U-74006F. Initial doses of U-74006F ranged from 0.01 to 30 mg/kg. Subsequent doses consisted of intravenous bolus injections followed by a continuous 42-hour intravenous infusion. Over the 48-hour treatment period, cats received total U-74006F doses ranging from 0.048 to 160 mg/kg. The animals were evaluated weekly for neurological recovery based upon an 11-point behavioral scale. With the exception of two cats in one group, the animals receiving accumulated doses of U-74006F (ranging from 1.6 to 160.0 mg/kg/48 hrs) exhibited nearly 75% of normal neurological function by 4 weeks after injury. Lower total doses of 0.16 and 0.48 mg/kg/48 hrs were associated with approximately 50% return of normal function, which was not significantly better than the recovery in the vehicle-treated control group. The lowest total dose tested (0.048 mg/kg/48 hrs) gave results indistinguishable from those in vehicle-treated cats, which had recovered only 20% of their preinjury neurological function by 4 weeks. These findings demonstrate that over a 100-fold range of doses, U-74006F has a remarkable capacity to promote functional recovery in spinal cord-injured cats.

Attenuation of hemorrhagic shock by the non-glucocorticoid 21-aminosteroid U74006F

The ability of the novel non-glucocorticoid 21-aminosteroid U74006F to protect against the development of hemorrhagic shock was examined in pentobarbital-anesthetized cats. The animals were hemorrhaged to a mean arterial blood pressure (MAP) of 45-50 mm Hg where they were held for 2 h. At the end of the hemorrhage period, either vehicle, a 30 mg/kg dose of methylprednisolone sodium succinate, or a 10 mg/kg dose of U74006F was administered i.v. followed by reinfusion of the shed blood. In vehicle-treated animals, there was a progressive post-reinfusion decline in the MAP over the subsequent 2 h. In the methylprednisolone-treated cats, the post-reinfusion decrease in the MAP was only slightly and not significantly better. In contrast, U74006F administration resulted in a significant maintenance of the MAP. These results suggest that U74006F may be efficacious for the attenuation of hemorrhagic shock and superior to conventional high dose glucocorticoid therapy in that context.

Modification of myocardial ischemic injury: a concentration response study of glucocorticoid supplementation during reperfusion

Reperfusion of the ischemic myocardium is routinely done during cardiac surgery and in the catheterization laboratory after acute regional ischemia. While reperfusion of the ischemic myocardium is necessary in order to regain full functional and biochemical recovery, the reperfusion by itself may aggravate the ischemic damage. Glucocorticoids have been shown to modify the outcome from ischemic injury in various experimental and clinical situations, but the results are conflicting. This protocol was performed using normothermic ischemic (30 minutes) isolated rat hearts, and postischemic reperfusion (30 minutes) with methylprednisolone sodium succinate (MPSS; 100-500-1,000 mg/L) was studied. All indices of myocardial function and all metabolic variables were significantly reduced after ischemia. MPSS (100 mg/L) improved dP/dTmax (recovery 68 +/- 3% v control 48 +/- 7%) and some of the other indices of left ventricular performance studied. MPSS (100 mg/L) also improved the tissue concentration of adenosine triphosphate (ATP) (13.8 +/- 0.5 mumol/g dry weight v control 11.3 +/- 0.8) and the total adenosine pool (16.8 +/- 0.7 mumol/g weight v control 13.9 +/- 0.8 mumol/g dry weight). MPSS (1,000 mg/L) impaired recovery of myocardial function (dP/dTmax, dP/dtmin, rate-pressure product [RPP]), increased tissue lactate (7.2 +/- 2.0 mumol/g dry weight v control 3.6 +/- 0.8), reduced glycogen (30.6 +/- 2.5 mumol/g dry weight v control 49.8 +/- 3.3), and energy charge (0.848 +/- 0.018 v control 0.890 +/- 0.010). It is concluded from the present experiments that modification of an ischemic injury by glucocorticoids given at the onset of reperfusion is possible, and that an optimal concentration of 100 mg/L exists for MPSS supplementation. MPSS in a concentration of 1,000 mg/L aggravated the reperfusion injury, probably by interference with cellular respiration.

Head trauma in the child

Head injury, either alone or in combination with multiple injuries, is common in children. Its pattern is different in children compared to adults, with diffuse cerebral swelling rather than localized hematoma being most common. The pathophysiology of pediatric head trauma is not yet clearly elucidated, but may be closely related to changes in the regulation of cerebral blood flow. The initial management and subsequent care of the child with severe brain injury are discussed from a multisystem viewpoint. The prognosis for children with severe head injury seems brighter than for adults, but there are not yet enough data to allow prediction of outcome in any individual case. Efforts to prevent, rather than treat, head injury in childhood are more likely to be beneficial.

Clinical pharmacological and therapeutic considerations in general intensive care. A review

The application of clinical pharmacological concepts and therapeutic standards in intensive care settings presents particularly difficult problems due to the lack of adequately controlled background information and the highly variable and rapidly evolving clinical conditions where drugs must be administered and their impact evaluated. In this review, an attempt has been made to discuss the available knowledge within the framework of a problem-oriented approach, which appears to provide a more clinically useful insight than a drug-centred review. Following a brief discussion of the scanty data and the most interesting models to which reference can be made from a pharmacokinetic point of view (the burn patient being taken as an example), the review concentrates on the main general intervention strategies in intensive care patients. These are based mainly on non-pharmacological measures (correction of fluid and electrolyte balance, total parenteral nutrition, enteral nutrition, oxygenation and ventilatory management) and are discussed with respect to the specific challenge they present in various clinical conditions and organ failure situations. In addition, 4 major selected clinical conditions where general management criteria and careful use of prophylactic and therapeutic drug treatments must interact to cope with the variety of presentations and problems are reviewed. These include: acute cerebral damage; anti-infective prophylaxis and therapy; cardiovascular emergencies; and problems of haemostasis. Each problem is analysed in such a way as to frame the pharmacological intervention in its broader context of the underlying (established or hypothesised) pathophysiology, with special attention being paid to those methodological issues which allow an appreciation of the degree of reliability of the data and the recommendations which appear to be practiced (often haphazardly) in intensive care units. The thorough review of the published literature provided (up to mid-1986) clearly shows that in this field the quality of randomised controlled and epidemiological studies is rather unsatisfactory. It would be highly beneficial to research and to clinical care if larger multicentric protocols and prospective epidemiological comparative investigations could be carried out to investigate more timely and adequately the variables which determine drug action, and the final outcome in the many subgroups of patients which must be considered in a proper stratification of intensive care unit populations.

Evaluation of an intensive methylprednisolone sodium succinate dosing regimen in experimental spinal cord injury

Beginning 30 minutes after compression trauma of the upper lumbar (L-2) spinal cord, cats were treated with either a high-dose regimen of methylprednisolone (MP) administered as the sodium salt of the 21-succinate ester (Solu-Medrol sterile powder) or the MP vehicle. Animals were randomly assigned to either treatment group (10 cats per group), and all personnel were blind as to which animals received vehicle or drug. The intensive 48-hour dosing regimen was designed to maintain therapeutic tissue levels of MP and consisted of an initial 30 mg/kg intravenous bolus of MP; 2 and 6 hours later additional 15 mg/kg MP doses were administered by intravenous bolus. Immediately following the bolus given at 6 hours, a continuous MP infusion of 2.5 mg/kg/hr was started. The infusion was stopped abruptly at 48 hours with no dose tapering. Animals in the vehicle group received an equivalent volume of MP vehicle. The total MP dose administered over 48 hours was 165 mg/kg. Animals were evaluated weekly for neurological recovery based upon a 12-point functional scale which assessed general mobility, running, and stair-climbing. Mean recovery scores at 1 month after injury (+/- standard error of the mean) were: vehicle group (seven cats) 3.7 +/- 0.9, and MP group (10 cats) 8.7 +/- 0.2; (p less than 0.001). Histological evaluation of the spinal cords revealed a strong negative correlation between neurological recovery and size of the spinal cord cavity at 1 month (r = -0.88). Three of 10 animals in the vehicle group became ill and had to be dropped from the study, whereas all of the 10 MP-treated animals survived in excellent health. The results demonstrate the therapeutic effectiveness and low incidence of side effects associated with an intensive MP dose regimen for treatment of experimental spinal cord injury.

The neuroendocrinology of physical injury

Physical injury of any sort--accidental injury, burns or elective surgery--provokes an immediate neuroendocrine response. Neural input arising from the cerebral cortex, damaged tissues and receptors detecting fluid loss leads to increased secretion of ACTH, growth hormone, prolactin and vasopressin from the pituitary, and to a general activation of the sympathetic nervous system, with rises in adrenaline and noradrenaline concentrations. Secondary changes include stimulation of cortisol and aldosterone and inhibition of insulin and somatomedin secretion. The glucagon concentration and plasma renin activity may also be increased, either immediately or after a delay. The duration of these responses generally depends upon the severity of the injury and differs considerably between hormones, for reasons that are not understood. The only endocrine changes consistently seen at later times after trauma are an increase in insulin secretion, which supersedes the initial suppression, and decreases in the concentrations of T3 and gonadal steroids. Some of the changes in steroid, thyroid and pancreatic hormones differ temporally or even qualitatively from those of their usual stimuli and are unexplained. The initial neuroendocrine response to injury can be construed as playing a defensive role, but the function of the later changes is not understood; it seems likely that they are adaptive in nature, but the scope for therapeutic intervention remains unclear.

Feedback action and tonic influence of corticosteroids on brain function: a concept arising from the heterogeneity of brain receptor systems

Two types of corticosteroid receptors can be distinguished in rat brain. The type 1 receptor resembles the kidney mineralocorticoid receptor and has two functional expressions in brain, i.e. type 1 corticosterone (CORT) preferring sites (CR) and mineralocorticoid receptors (MR). The type 2 receptor is similar to the liver glucocorticoid receptor (GR). CORT binds to both CR and GR. The localization, binding specificity, and capacity of the receptor systems have served as criteria to evaluate steroid dependent events in brain biochemistry and behaviour. The GR is widely distributed in neurons and glial cells, with the highest density in frontal brain regions. The GR becomes occupied concomitant with rising plasma CORT levels after stress and as part of the circadian rhythm. The GR mediates the feedback action of CORT on stress-activated brain processes. The CR has its predominant localization in neurons of the septo-hippocampal complex and has a ten-fold higher affinity for CORT than that of the GR. The CR is, at all times of intact adrenocortical secretion, 90% or more occupied by endogenous hormone. The CR mediates a tonic influence exerted with stringent specificity by CORT on hippocampus-associated functions, e.g. cognition, mood, and affect. CORT, via the CR, thus contributes to hippocampus function in interpretation of sensory information, leading to appropriate neuroendocrine and behavioural responses, which are themselves subsequently subject to feedback action via the GR. The MR mediates the mineralocorticoid effect on salt and water balance and its behavioural corollary of salt appetite. The anatomical localization of the MR system is as yet ill-defined, although functional studies suggest circumventricular organs as mineralocorticoid target sites. The CR and the MR have in common the high affinity for mineralocorticoids, but the CR is defined by its exclusive responsiveness to CORT as its agonist. The CR and MR probably represent the same chemical receptor modality (type 1), which is expressed differentially depending on the presence of extravascular corticosteroid binding globulin (CBG) in the vicinity of the receptor. GR capacity is subject to autoregulation. Chronic stress, senescence, and chronic CORT administration reduce GR number, with, as a consequence, a less efficient feedback signal. The CR number seems not to be under the control of corticosteroids, probably since the receptor sites are extensively occupied by endogenous hormones. The CR number displays a circadian rhythm and is reduced during senescence.(ABSTRACT TRUNCATED AT 400 WORDS)

Recovery of function after brain damage: severe and chronic disruption by diazepam

Following unilateral damage to the anterior-medial region of the neocortex (AMC) in rats a sensory asymmetry appeared, but recovered within a week. In a separate group of rats with AMC lesions daily 3-week exposure to diazepam (Valium, 5 mg/kg) beginning 12 h after surgery caused recovery to be delayed indefinitely. The efficiency and speed (as opposed to symmetry) of behavior was not impaired. More than 9 weeks after discontinuation of diazepam (12 weeks postsurgery), recovery was still not apparent. Postmortem analysis ruled out lesion size as a contributing factor. In a second experiment undrugged animals with AMC lesions were allowed to recover for at least 3 weeks before being exposed to diazepam. These animals showed only a transient (2-day) reinstatement of asymmetry despite continuous drug treatment. We conclude that important mechanisms serving recovery of function may be vulnerable during a short period soon after brain damage.

Acute effects of dexamethasone on normal and on posttraumatic spinal cord polysynaptic reflex activity and axonal conduction

The effects of a single intravenous injection of a high dose of dexamethasone (4 mg/kg) on polysynaptic reflex activity and axonal conduction were measured for 5 hours in the intact and in the compression-injured L-7 spinal cord segment of high spinal cats. The segment was injured by a transient compression of preset degree and duration. In the uninjured preparation, dexamethasone administration significantly reduced polysynaptic reflex size for 2 hours. Axonal conduction was unaltered. One group of injured animals was given dexamethasone 30 minutes after trauma, whereas another was not treated. The acute posttraumatic changes in both parameters did not differ significantly in treated and untreated animals. Histopathologically, differences in the amount of segmental edema and hemorrhage between untreated and treated animals were not significant.